Descartes’s Doubt

Descartes

But what, then, am I? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts, understands, [conceives], affirms, denies, wills, refuses; that imagines also, and perceives.

II. Cartesian Doubt

A. Methodological Skepticism

What does it mean to be certain?

Certainty means inability to doubt

So subject all beliefs to doubt to find the foundation that is undoubtable